Toshiba c660 Ram Upgrade

Hello, im new to this community Yoroshiku.

i recently gotten a old Toshiba Satellite C660-20j Link of the laptop that my friend just wanted to throw away, so i asked her if i could have it. It's old but i still use a much older laptop for browsing and editing documents and it's ok for me, so i wanted to give this to my niece for her school work.

I had a bad experience in buying Ram for another laptop so im not quite sure specially now im buying it online (so i can't test it). So i was hoping for all of your Guidance and Opinions if this is right/compatible with this laptop.

As it said in the Link of the laptop it only stated
"maximum expandability : 8,192 MB
technology : DDR3 RAM (1,333 MHz)"

this is the Ram i have inside the laptop (2GB + 1GB) Cpu-z

Memory ~ 1 Gb Ram ~ 2 Gb Ram

Link for Samsung Ram

Question:

1. Why does the Ram says in Max Bandwidth = PC3 10700 (667Mhz), when i searched for DDR3 1333 = PC3 10600 ??
2. Why is it 667Mhz? isn't it supposed to be 1333 Mhz??
3. Why does in the Samsung website state that Voltage 1.5 / 1.35V? is it DDR3L??
4. Can i Buy a DDR3L so it's much safer voltage wise? (you know, so it can either be 1.35v or 1.5v)

What i want to buy:

This is the shop Link , Just a 4 GB Ram. so i can have this laptop run a 6 GB Ram total.

I know it's a cheap Ram or an unheard of brand, but SK Hynix and Kllisre are quite Reputable in China (according to my friend there). and as im just gonna give this to my niece i don't want to go over much more expenses (btw the keyboard does not work and it has no battery. But i already ordered the parts so im just gonna install those). the ram is the one thing i wasn't 100% sure compatible or right for the laptop.

thank you in advance for the help