Aqeedah of Salafis

Q: Some Ulama from the Deobandi school of thought have included the Salafis as a part of Ahlus Sunnah Wal Jamaa'ah and some haven't. They have done this primarily on the basis of Aqeedah. Someone also told me that Moulana Husayn Ahmed Madani had some 'Salafi' beliefs specifically regarding Aqeedah. After some searching I found it to be true.  If that is the case, and their Aqeedah is also correct, why should we then regard them as deviated? Isn't it just another valid ikhtilaaf from many. 

My second question is that, is there Ijmaa' on the compulsion of following a Mazhab, or is it only for the betterment of this pure Deen of ours?

Taking back a gift

Q: Married sisters gifted their share of property which they received from their father to their brother. After 2 years some dispute occured between the brothers wife and sisters, and now they are saying to return their property.

Is it allowed to take back the gift which they have done earlier?

Greeting with salaam alaikum

Q: Is it ok to just say سلام عليكم? In Hayaatus Sahaabah (Part 2), under chapter 9 -

خروج الصحابة رضي الله عنهم من الشهوات - :التسليم على المسلم - عمل ابي امامة رضي الله عنه في ذالك

A riwaayah comes wherein Abu Umaamah رضي الله عنه said this.

Heartache after a close friendship breaks

Q: I am a Muslim girl and I am really suffering from heartache. I had a female best friend. She was more than a sister to me and I love her so much. I really wanted her to be in my life forever but today she said to me that she will not contact me from now on. She really wants to end my part in her life. I am so used to her that I am feeling like I have lost everything by losing her. She just said that she will text me once in a while but will not share the bond we used to share. I am so disturb. I really want her back in my life. Please advise me.