Would it prevent third eye progress?
It depends on the type of meditation being done.
A mind stopping meditation would be quite futile on caffeine (I’ve tried) but a one pointed focus meditation can be strengthened.
What do you mean Exactly when you futile?
Futile. It means pointless; incapable of producing a useful result. In other words, it won’t work.
When you meditate, you become more aware of your body. Introducing a drug into the progress will likely make you more aware of its effects on your body. So I can see taking caffeine pills prior to meditation causing you to possibly become more jittery and unable to focus while meditating. It is actually part of the reason I make a point not to smoke prior to meditation/ritual
But it really depends on you and your body
I don’t think it would hinder progress with your third eye but as C.Wilson said, it’s likely going to make it harder to ignore the workings of your body. If you have ADHD or something it might help you focus, otherwise it’s probably going to make it harder to concentrate and slip into a trance state.
You can meditate on anything there’s no obstacle if meditation is a focal point
Yes, of course you can… it just might be harder to relax but honestly I have to take various medications and I have no problem meditating on any
I’d suggest using bineaural beats to help your brain sync into whichever state you’re wanting and sometimes I use guided ones first if I’m needing extra help to slow my thoughts and focus