What Tiur said about this is correct. Prior to 0.22 it's only possible to get on to 3 routes, and one of those is Sasha's slave route. The other two being Cassie and Riley. In 0.22 it is possible to officially get onto routes with 4 girls, those being the ones you mentioned in a later comment. That's not to say that all of the routes for those girls have been available yet, for example there's no way in 0.22 to actually start Hikari's slave route, nor Cassie's sub or slave route. Obviously these things will be possible, just not 0.22.
To be clear, the current routes it's possible to actually start (And so have show up on the save file) are...
You can however get quite close to starting a few other routes not listed here by the end of 0.22, but the actual start of them will be in future updates.
The lesbian content so far is always without MC, however the plan is that if you let them play with each other alone, they'll do it in threesomes too. Since the only girl who's actually into girls at this stage is Cassie, I don't plan to have the other girls suddenly ok with doing lesbian stuff just because MC is there. Threesomes will still happen when lesbian content is disabled, but what happens in them will be far more limited.
However, we're yet to get to the first threesome scene, so this is subject to change. There isn't even any actual lesbian scenes in 0.22, though one of them does get kinda close, and some of the scenes do set up future lesbian stuff (If the player chooses to do so). Considering it's possible to tell Cassie it's fine for her to do lesbian stuff, but then actually just opt out of all lesbian scenes when they come up, I need to think of a way to ensure logical consistency when it comes to lesbian content in threesomes. It'll likely be determined by whether you played the previous lesbian scenes, rather than whether you told Cassie she could have some fun.
The "Selfish MC mode" setting in the settings menu overrides this though. That mode is for people who cannot tolerate anything that implies any of the characters aren't straight, and it basically retcons the game so that Cassie isn't even bi. Considering you can skip lesbian content anyway, I wouldn't recommend using that setting unless even the mention of lesbian content being possible makes you uncomfortable for whatever reason.
(Also due to how the setting works, accidentally leaving it enabled will remove lesbian stuff from any save file you load with it enabled. Recommended not to touch it at all for most players, even those who want to skip lesbian content.)