When you sub you only get that month, you can buy previous months, but each creator has the option to set it up differently. Some have it turned off, some have it so that if you buy the highest tier you get to see the lower ones, and some have it so that each tier is separate I believe (that last one might have changed). There's also a system that some creators use where you can see the content from any previous month that you had access to on resub. So if I sub in January, then don't renew in February, I can't see January anymore. Then if I sub in March, I can see March, and January again. Not all creators use this system.
As for if we can see anything in that pic? Somewhat? She blurred out the crotch in previous pics so maybe, but it's hard to see.