Lithium Battery Complications

Greetings all. I'm new to solar and wish to install a system on our travel trailer. Sitting down yesterday with the RV service guy, I realize I'm not yet ready. I had intended AGM batteries, now I'm considering Lithium. My immediate questions are these:
1) It seems I now need a solar controller intended for lithium batteries. Is that correct?
2) Victron advertises its batteries as having just four cells. Of course I don't want a battery consisting of a hundred smaller cells. Which battery brands do you recommend?
3) Can two separate Li batteries be wired in parallel? I read that there are inherent troubles with this.
4) Finally, if I find myself with cold-soaked Li batteries...let's say 15 degrees fahrenheit...what sort of power would I have? Enough to run a heater blower long enough to warm the trailer/battery? (2X Battle Born 100Ah 12VLiFePO4) How cold is too cold for cold soak?
5) Is it true that a Li battery should never be charged below 32 degrees F?
FYI: 4X 170-watt solar panels in series, Victron MPPT 150/60 TR controller, AIMS 2000 watt 70A inverter/charger, 2X Battle Born 12V LiFePO4 batteries
Thank you for responding.
Comments
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
Battleborne kit https://battlebornbatteries.com/shop/adventure-in-a-backpack-200ah-amp-lithium-bundle/
This link https://forum.solar-electric.com/discussion/352589/lithum-battle-born-battery-claims-of-peformamce-and-origin#latest is where I previously contacted Battleborne asking some general questions.
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
Blanket statements can be potentially dangerous, Li batteries ( a collection of cells or cell blocks connected in series to achieve a desired nominal voltage ) can be connected in parallel as long as there is a separate BMS for each battery. Without a BMS the potential for disaster is greatly increased. Over and under voltage can damage cells, the rate if voltage change at the knees of the charge/discharge curve is very rapid, a couple seconds is all it takes to destroy the battery without protection.
There are way better resources for information than youtube by the way.
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.