Xexun Tk-102

i have some questions.if you answer i will be thankful.

1-i am confused as some say tk102(genuine xexun) can track -floors of a car park and some say it cannot find more than 3-4 satellites even without obstacles.i want to track my children and in case of an abduction device must work inside trunk or with other obstacles with good accuracy.

2-is it too hard to add an external gps antenna.i dont know much about electronics.

3-is it too hard to modify/change power source to extend working time?there was a 12000mah battery for tk102 on ebay claiming to last 1 months.this battery can be plugged to usb but if it is not possible how can this be achieved

4-how is tk102 and other gsm trackers accuracy , ability to work with obstacles compared to cell phones.cell phones have agps does it make difference and how reliable cell phone softwares are

5-can you advice other devices with better gps (especially accuracy and ability to work obstacle).max 200$ including shipping.i will only use sms autoreport and perhaps gprs autoreport mode so other modes are not essential.not essential but a well known device would be better so i can find info at forums before and after buying.