1. I don't know which one you referred to. If it's Gacha for Royal Ending, it just stay there for 3 days only
And if it's Royal Ending, as long as you don't finish the story yet, and not making Royal Gacha come up, you can stay in that place forever while switching to other prince story
After that you can go back to continue Leon story
Just remember, every time you switch route or re-play a route, you need certain ticket which usually only you get after finishing a route
2. To get Royal Ending, you don't need to buy sweet route
Only having sufficient amount PLUS Rare Item from ROyal Gacha (which usually the wedding dress) that you need to spin with gacha ticket
Make sure you have enough to buy all item first since Arithmethic always made us get the dress the last (if I'm not wrong you need to prepare 8-9 gacha tickets)
And Sweet memory and premium item doesn't raise your affection, only your charm
3. The same answer, memories doesn't raise your affection. If anything, the one raise your affection is item from spinning HIS gacha from garden AND item from Royal Gacha which having affection attached to them
You can also raise his affection by spinning certain gacha (try to check every gacha available)
and to get them you need gacha ticket, too
4. I saw his route been renewed so I don't know if old answer still applicable here
If you don't see here, try to go to otome obsessed website
Since it's been long time I play this game, I kind of forgot how we get gacha ticket
Did we get it one from login sheet or only from ranking in the event
Anyway...the one I know hard to get in this one is closet space
There's no one in the login sheet (even the gold one), only 5x closet from ranking in event and sometimes from special gacha that give you 20x closet
still...we'll need more gacha ticket for that one...and it's kind of gambling when we'll actually get what we want
Good luck there
You don't have to pay any penny to play this game as long as you patient enough to get freebies from doing something...currently they will push you seeing some video (then you get 1 coins)
or if you diligent enough to rank in every event