My questions are so basic I must be a dumbass but,

What rounds get drafted on each draft day?

I have early picks - if I move players into the manual draft column in the middle is that the order that they will be picked from rather than mess around with sliders etc?

How do you extend a contract without changing the current contract - future seasons only as it were?

Generally drafts go:
Day 1: 1st round
Day 2: 2nd round
Day 3: 3rd and 4th round
Day 4: 5th, 6th, and 7th round

Yes, provided those players are available, the middle column will be who is actually drafted when your pick comes around.

You will have to manually change the current years base and bonus values to extend them in that manner.

A small tip for extending players, offer the player a 0% bonus contract. The player will not accept it, however will tell you the minimum amount of bonus money they want on their next deal. Then max out the bonus slider to 75%, change the length of the contract to fit the players timeline (players speed and other intangibles decrease over time as they hit 30) and change the base salary slider until bonus money is above the minimum threshold the player requires

Below is a link to the XFL's help thread when important info is shared including my own unfinished help guide.

https://xfl.myfootballnow.com/forums/4

My guide

https://xfl.myfootballnow.com/forums/4/1129?page=1#9505

I have an other basic question so I will use this topic to ask...

Why a player, a defensive end for example, can have a 90/90 rating for LDE, and 85/90 for RDE while also having a 100% XP as RDE ? What justify the 5 points difference then ?

Lots of players have a preferred side, even in real life NFL. Some OL are only comfortable playing right tackle, etc.

If you want the ratings points to be higher, switch the players position and with time, he should end up 90/90.

I'm assuming the player is a LDE???

Switch him to RDE and he shouldn't almost immediately become a 90/90 RDE and 85/90 LDE.

I'm not exactly sure why it does that but the player always seems to end up better at his "designated" position and just below maximum at his off position. The same goes for LBs and DBs.

Yes, this happens...also does with OL.