When to use GPS Warm Start and COLD Start

Hi,
I am using Quectel L86 module, in that module warm,hot,cold Start options are in that device. My query are following,
1. When wanted to use these Starts.
2. After these Starts, Even though I didn't get satellite connectivity .... How long, I need to wait to resend these Start commands.
3. Which of these following satellites, I need to enable:- (All I need to enable or according to my location I need to turn ON/OFF)
* GALILEO_FULL_Enable
* GALILEO_Enable
* GLONASS_Enable
* GPS_Enable
4. Even in 12-15 Satellites View also.... The GPS not giving same location repeatedly...... It is giving lat&log difference of 15 meters....

Help me to solve these problems as soon as possible.

It is giving lat&log difference of 15 meters....

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Sounds fair. Sure you understand expectable GPS performance?

I am using a different one.
GPS Module with Ceramic Antenna for DIY Handheld Positioning System for $7.86
https://www.dx.com/p/open-smart-gps...ino-apm2-5-flight-control-480918#.WiDKElWnH4Y
I don't have a cold / hot start option but it does get good data faster if it is restarted after being on. I would say use cold start except after a reset. Does it tell you when it has enough satellites and the data is good?
Without moving, the Latitude & Longitude numbers go up and down independently. It seems like it is wandering around but stays within a 25 feet diameter circle. I guess that is pretty good trying to triangulate my location from 3 or more moving objects in space.

Just out of curiosity, I tested this GPS Module. I took a few sets of data with a Stationary GPS sampling once per second then plotted the 3 least significant digits in Excel.