Questions about Summoning mechanics

[King Of Clouds]

I've noticed some issues and open questions regarding some summoning mechanics, so I wanted to make a thread to ask about them.

First of all, I read from the Wiki that Blackguard Create Undead uses Animal Slot:
https://wiki.bgtscc.net/index.php?title=Blackguard

While testing this out in game, it seemed like it actually uses the Summon slot instead, as the skeleton disappeared when I tried to conjure a creature with Planar Binding. On the other hand, in the Summong wiki page it seems like Blackguard's Hellhound (lv 10 Summon Fiend?) uses Cohort slot, whereas in the Blackguard page it says that the Fiend uses Summon slot. On the other hand there's some other, partially conflicting information about summoning in the general page: https://wiki.bgtscc.net/index.php?title=Summoning

My questions regarding the Blackguard summons are:
1.1) What slot does the skeleton use?
1.2) What slot does the fiend use?

I also wanted to ask about the familiars as the Familiar page states that familiars of epic casters get a spell like ability from list of lv 1-3 spells, which is further improved with the "Improved Familiar" feat (source: https://wiki.bgtscc.net/index.php?title=Familiar). A few clarifying questions:
2.1) What are these spell-like abilities exactly? Is there a list somewhere and does the ability work 1/day or somehow else?
2.2) Does the "epic level caster" refer to non-multiclassed pure wiz/sor, or does the progress stack somehow with PrC's?
2.3) Does the "Improved Familiar" offer new familiar options, or does it just give the additional levels for spell-like abilities?

Any answers to even some of these questions would be highly appreciated!

[Glowfire]

2.1) What are these spell-like abilities exactly? Is there a list somewhere and does the ability work 1/day or somehow else?

You call for your familiar and each time you choose what spell-like abilities they can cast. Some are 4 times a day and some are 2 times. It depends on the spell level. The higher the spell, the less uses there will be.

2.3) Does the "Improved Familiar" offer new familiar options, or does it just give the additional levels for spell-like abilities?

There's some new familiars such as imp, faerie dragon, pseudo dragon, mephits and a few others.