Any of your standard stretching routines should work. I would make sure to focus on areas where you seem to have trouble. If your hamstrings or hip flexors are tight, give them extra stretching work. The neat thing about flexibility is that as you get stronger you'll become more flexible as well.

People tend to be stiff because of weak muscle groups. Not necessarily because their muscles and tendons are tight. Sometimes an opposing muscle group is not strong enough to pull the muscles you're trying to stretch. For instance the hanging leg raise is a good example. You might be able to have straight legs sitting on the floor, but if you try to raise them from a hanging position they want to bend. This is because the core and hip flexors are weak. Not because a group of muscles are inflexible.
I am sure there are some face stretching that might lead to more wrinkles, However, I believe some Facial Gymnastics are helpful to prevent wrinkles.

My mother had deep marionette lines (lines from her nose along the sides of her mouth).my facial structure is like hers. However, occasionally -at least weekly- i do a yoga’s stretch called, I think, i think. The Lion Stretch. This stretches the face in a way that I think use some muscles that otherwise not often get exercised. In any case, I am 70 and thus far those lines have not formed on me.his is a ‘it depends’ answer. If you push your body beyond the capable limits and hurt yourself in the process. Yes it’s dangerous. But if there’s a subtle increase day by day and week by week the stretching process over a long amount of time will have your body adopt the new (more flexible) normal in an appropriate fashion.

Imagine if I had a hypothetical rubber band that would be similar to a muscle if I pulled it way too hard too fast it would snap but if I slowly increased the stretch, let it rest, and then pushed the limits more and more. It could reasonably extend to a more stretched length versus the rapid pull.
gymnastic stretching.

https://easyflexibility.mykajabi.com/forearm-stand-pincha-mayurasana-feathered-peacock