You have half guard on his R leg. He has the far side underhook and crossface.
If your feet are on the outside of his R leg, you can turn into him.
If you move them to the inside, turn onto your L hip and reach back with your R foot to snag his L leg. If you do not move on to your L hip, you cannot reach back as far with your R foot. with his R foot trapped, square up, grab his L tricep with your R hand and bridge and roll him to your R. You could trap his foot, he could go to mount and this would still work so in a way you are just preempting the bridge and roll from mount.
If he hides his L foot, move your feet back to the outside and turn onto your R hip. Drive your L knee into his R hip, extend your torso away, and work for the Z guard - L foot near his R hip to guard against footlocks, L knee on his R shoulder keeping him at bay. He should feel a need to back off a bit to keep his base. Get a dog paddle grip on his L arm with both hands to stop him crossfacing.
He is on his knees, you are sitting in front of him on your R butt cheek and up on you r hand. Grab his L collar with your R and slide your R foot betweeen his knees, pulling him in and yourself toward him. Hook behind his R knee with your R leg. Your L knee is up on his R ribs, fairly high so you have structure to prevent him pushing the knee down and putting his weight on you. Your L foot should be kept low, near his hip to avoid footlock attempts. You can lock the feet per closed guard (side note - Pete King showed me that the lock is much stronger when the ankles are crossed one way than when they are crossed the other - I can't remember which offhand but it is a matter of a simple experiment to find out)
Getting the back
Your L knee can be easily replaced with your L underhook. Swim it through and come up on your R elbow, then hand. Your L ear should be on his chest. Turn to your R and use the R leg to drag his R knee to his R as you shuck his shoulder over your head with a shot put movement of your L arm. Dragging his knee out makes getting the back much easier. You probably need to release the leg hook for maximum effectiveness - it is dragging the knee rather than keeping the hook that is most important. Climbing onto his back can be difficult. get a seat belt grip over his R shoulder, put your weight on his R shoulder and roll him onto his R side. Get hooks, "staple" his head, etc.
His R arm is over your L shin. Hold his R tricep in place on your shin with your L cupped hand and get a grip on his R sleeve with your R hand. "Rip" his sleeve to the floor similar to an arm drag, drag his knee out with your R foot as before and take the back.
(didn't do this on 21/10)
As before in Z guard, his arm over your shin. Let your L knee move out to your L so it is in the crook of his R elbow. Cup his tricep between your knee and his shoulder with your L hand. Drive the L knee (do not extend your leg and push with the shin) over the top of his R elbow, pull the R arm between your bodies with your L hand as you come up on your R hand. Leg drag and take the back from here.
In Z guard. He overhooks your L leg with his R arm and starts pressing your L knee down to start a pass. Pull your knee toward your chest and the floor at a downward angle to free it, then circle it outside and behind him like a crescent kick, coming up on your R hand and taking his back. The knee should move at a downward angle - you don't want to knee him in the face - even for purely selfish reasons, his head getting in the way will stop you getting what you want.
You get the underhook from Z guard as before. He overhook/wizzers your L arm with his R. Grab his R hand with your L and pin his R forearm to your chest with your L tricep/elbow/armpit. Dive your head toward his R hip and reach between his legs with your R hand, underhooking his L leg as you drive back hard with your L elbow and roll him over you to your R. Most of the power comes from your L arm/elbow, but the R adductor and R hand pushing him over also contribute. You do not take him directly to the side, rather move yourself out of the way and put him where you used to be.
(To understand a technique, you should understand the function and appropriate use of all four limbs in contributing to the technique. Also, understanding the exact angles required for proper execution of a technique is essential for mastery).
From Z guard, move your R foot inside his R leg - but the heel is on the floor and the toes up so you still retain some sort of grip on his shin with your foot ("hockey stick"). Drag his shin right out to your L with your R foot until his R leg is straight. Step over it with your L foot, wrap it up with both arms and do a single leg takedown on him - reaching out for his L knee and ankle will helf complete the takedown. (Similar to pulling deep half guard from Z guard and doing Jeff Glover’s “Homer Simpson” sweep on him, except that you are using an effective shortcut of that).
Back Rolling Sweep
From Z guard, R hand grabs his pants near the knee, L hand grabs his L sleeve. Come up on your R elbow and push his L hand out to his L to encourage him to push back. Roll back, bring your L hand in a big circle around to your L hip as you load him up on your L shin. Kick back overhead and roll back over your L shoulder holding on with the R hook so his bodyweight pulls you over the top and into half guard top.
Even if a technique seems difficult or weird at first, perseverance furthers - practising it take you places you haven't been before and expands your experience and capabilities.
From the Z guard with your hands in dog paddle position on his L arm, cup his tricep near his shoulder with your L hand. Your R hand is near his wrist. Collapse your L leg and pull his shoulder down to your chest with your L hand. Your R elbow lifts up to completely isolate his R hand, stopping him from grabbing his belt or doing other defence. Get the kimura grip. Move your hips to the R and get the lockdown on his R leg. Keep moving to the R and turning on your L hip until his L shoulder is on the floor. This takes all the play out of the shoulder and the kimura comes on very quickly. Go slow and smooth when practising - in this position, there is no play in th shoulder at all and jerky movements may result in injury.
Spin-under Omoplata from Z guard
He overhooks your L thigh with his R arm in an attempt to smash your knees down and pass. Grab his R sleeve with your L hand, under the leg. Move your hips away from him, take your R leg out from between his and put it on the outside of his R knee. Do a little situp and move your head toward him. At the same time, pull your R elbow underneath your body, get on your R shoulder, come up on your R toes and duck your head under to spin under to the inverted position. You are now in a position to roll forward, drive his R shoulder to the mat with your hips, and sit up for the omoplata.