Here's an answer to question 1:
**broken link removed**
Scroll down to MELF type resistors and click on "MLT".
You might get more answers by going to their home page and looking around.
Thanks Ron. Its exactly the info I am looking for.
Because positive TC 'MLT" and "LT" type resistors in the above weblink are classified in distinct catalogs, it leads me to believe that most common MF25 metal film resistors all have negative temperature coefficient unless someone else points out otherwise.
Interestingly, the TC of these positive TC metal film resistors get smaller with higher ohmic values and so now I am wondering whether this generalisation also applies to common MF25 metal film resistors.