1. Which are the limits for follow/unfollow per day? But the max limit? Can I follow/unfollow on the same day?
The max following limit is 1k/day, Twitter introduced some changes to this not too long ago, which doesn't seem to effect every account of mine. I couldn't really figured it out the reason behind this so far. I have accs which still can follow 1k/day, others don't and i use the exact same settings for all of them. There are not published hourly limits too.
I'd say the safe limit for your account age is 500-600 follows per day, this is when you won't even get password resets or just rarely.
There's also a following wall at 5k, you aren't allowed to follow more than that until you have 5k followers.
There's no limit for unfollowing whatsoever. You can follow, unfollow on the same day safely. I don't follow/unfollow at the same time with the same account though.
My daily routine consists of following 1k (where i can) and unfollowing 1k on the same day, password resets here and there, but nothing too serious, lately i hardly get any. These accs i'm using at the moment are just a few months old too.
2. How to avoid being ghosted? (I follow someone but that person doesnt get the notification)
This kind of ghosting won't happen on Twitter no matter what you do. Ghosting on Twitter means that you're ghosted from the Twitter Search, so your tweets don't turn up there at all when people search for keywords, hashtags. For the most part this can be avoided if you don't post the same tweet over and over again on the same account or between different accs. And it usually only lasts for 24 hours, serious violation can cause your acc to be excluded from the Twitter Search for good, but even in this case, your followers or anybody who visits your profile will still be able to see your tweets.
3. How many accs with the same link?
There are different opinions about this, i personally go with 1 domain per account. Others use more, even a lot more.
It's pretty hard to get your accs suspended for good, if you do something against the rules, it's almost always "just" a password reset either via email or phone. Permanent suspension is caused by ip violations in most cases, if you use too many accs on the same ip, been there, done that lol
How many accs on the same ip is too many? 10 for sure
You can follow the same account per proxy rule, what you follow on instagram. I personally use 2 accs per proxy.
Make yourself familiar with the
Twitter rules and
best practices, that will spare you a lot of headaches.
I'd say Twitter is still one of the easiest, if not the easiest site to game.
GL