Yes, all of your Pokemon can go up to 34.5 in that case.
There are plenty of Pokemon Go IV calculators online that will tell you the exact level - you plug the Pokemon's CP and a bunch of other data into the calculator and it spits out the Pokemon's exact stats, including its level.
There's no way to precisely determine a Pokemon's level within the game itself. The exceptions are for special situations:
Special situation 1: egg hatches - if you are at level 33, or any other level above 20, all of your hatches will be at level 20).
Special situation 2: maxed-out Pokemon. If you are at trainer level 26 and repeatedly power up a Pokemon until the "Power Up" button is disabled with the "Trainer Level is too low to Power Up" message, you can be assured that your Pokemon is now at 27.5.