Hi Iko! To answer a few of your questions:
1)"I was expecting the massage would be done with warmed-up hands rather than stone cold hands"
~While most therapists would obviously not want to put freezing cold hands on a client, it may have been as simple as he didn't realize how cold they were, or thought they would warm up quickly during your session. Either way, next time, Before your session begins, tell your therapist you do not like cold hands. Ask them to run their hands under warm water prior to your massage, or to use warmed oil or lotion. You could also consider using a heat pack, or hot stones during your massage for added warmth.
2) "he claims himself a qualified therapist" "Who could i contact to check if he is decent professional??"
I am assuming you saw this therapist at a private residence? Most states require licensure for massage therapy (but some DONT). Google your state massage therapy board, you can call them or search their online database (if they have one) for the therapists name. Their license # and when it expires should be listed publicly. You can also check with AMTA, or ABMP which are 2 large massage insurance providers, they list therapists by state (but keep in mind he may use different coverage). You can also use the NCBTMB which is a national accrediting association for therapists by state (but remember not all states require this certification, it is voluntary for some).
3) "Also, this man spent a little too long on my bum compare to other areas of body, although I requested him to focus on my calves to improve blood circulation."
Please know this, you may ALWAYS speak up during your session if you are not comfortable. It can be as simple as saying "That doesn't feel good, can you move on to a different area", or "I'm not comfortable with you working on that area, please move on". You also have the right to end a session and file a complaint with the State massage board if you feel that something is inappropriate.
That being said, the muscles of the legs work in conjunction with others, working on the glutes and upper leg can help relieve tension and can release fascial restrictions. Maybe he felt some areas of tightness and decided to work the entire region, just remember that it is YOUR massage, and a professional will never be "mad" if you want them to work somewhere else. Many professionals choose to work on the glutes though a sheet to provide relief, but also more modesty and comfort for those who want it.
4) "I was also asked to sign the questionnaire i answered. was it really necessary?"
Yes absolutely. Almost every state requires that you fill out proper paperwork, as legally, massage is considered healthcare. In the event of a problem (such as a lawsuit) therapists can submit their paperwork to prove what did or did not occur during a session. (ie.. Client comes in with a bruise on their arm, the therapist notices, and avoids it during the massage. Afterwards, the therapist does not annotate it on the form. He later receives a lawsuit stating he bruised and damaged a client. See how a little note would have helped?)
It also helps us track a clients progress, frequency of sessions, health history like medication or surgeries, etc!