[HELP] Hashcat Mask

Hello,

So i need some help for create a mask.
Here is what i know about the password:

1: It's a 8 chars uppercase password
2: the password never have two same caractere next to the other like AABCDEFG
3: The password don't have more than two time the same letter in the whole password ABCABCA can not work because there are 3 time the A letter in the whole password but ABCABCD work.

4: the same sequence is never repeted in the password: ABHGJAB is not possible AB is repeted.

I don't know if the mask will really decrease the cracking time but i have 50.000 H/s cracking speed so if you can calculate it too it would be very nice.

Thank you very much !