Sizing BatteriesIF there is room [physically] for an 850mAH battery to fit instead of a 700mAH battery, and it is the same type of battery [Lead-Acid, Ni-Cad, Gel Cell, etc.] then yes you can make the substitution. The 850mAH battery is just electrically slightly larger than the 700mAH battery. The numerical designations for the two battery examples you give in your question mean that the first battery will deliver 700 milliamps [700/1000th of an Amp] for a period of one hour. The same is true for the second battery except that it will delivery slightly more current[850mA] for one hour, or the same 700mAH rate for a slightly longer time.
yes
INSTEAD
you can use or , otherwise, or rather than.
what can i use instead of glyerin in making tootpaste
You Can Use Paper Bags Instead Of Plastic
We could use leather instead.
No problem if it's the same voltage, it will just last longer. But it might be significantly bigger, which could be a problem.
You can use "want to" to express a desire or intention to do something (e.g., "I want to go to the beach"). "Going to" is used to talk about future plans or predictions based on current evidence or intentions (e.g., "I am going to study for my exams").
Will, when, why, it, can
You could not use lightning instead of batteries.
For thickening soups, stews, and gravies, you can use flour instead of cornstarch.