Under Windows x64 I jumped straight from ver. 2.87 to 3.19 and now to 3.24.
With ver. 2.87 it's OK.
But there's problem with those 3.xx versions:
I have a list of ~100 trackers which sometime I use.
This list is divided into let say 10 groups by 10 trackers.
Under ver. 2.87 if I select all trackers, right click and choose 'Announce' then every single tracker is announcing.
But under 3.xx only first tracker from each group is announcing and I can't even manually announce any of the rest trackers.

(Link removed by Mod and sent to Devs : Please re-post pic with all trackers blurred)

I assume that's how every client works, and how they should work according to the rules.

Groups can be used for multi-tracker announcements. All URLs in a group are considered interchangeable front-ends for the same entity, and client can choose which one to use at random.

Note that unless you use some private infrastructure that relies on “registration” of torrents on trackers to operate, there is no sense in announcing to dozens of public trackers. Chances that there is some lone seeder which doesn't use DHT but adds random trackers to torrents are close to zero. Moreover, if they exist, they likely use very limited internet connection or tunnel with outward TCP only. You have to have a direct connection with open port for them to be able to connect to you.

I'm sorry but you didn't understand - up to ver. 2.87 it works.
With 3.xx versions - it doesn't work.
I'd like to have this feature working back again.

It was a bug, not a feature.

However, there is only a de facto standard, as multi-tracker announcements are rarely implemented as written:
http://bittorrent.org/beps/bep_0012.html
https://github.com/bittorrent/bittorrent.org/issues/82
However, the division between first order groups and second order groups is still respected.

You can mass-edit the tracker data to put each link into its own group, then the client should update all trackers equally. I'm more interested in learning which kind of activity might actually use that setup, though.

You failed again - it is a feature not a bug because it's called by purpose 'Multi-tracker group mode.'