So basically what Mirror mode is, you run the original OSRS Client and launch up OSBot and run it with Mirror Mode, it'll then attach itself to the OSRS Client and bot via that rather than OSBot's Stealth Injection client. I only ever bot using mirror mode as I'm alot more successful with that than Stealth.
Not sure why you can't talk on the Discord though, maybe you need to be verified first. You can do that by posting your Discord user here;
Not sure how you can't work this out yourself, but...
50k p/h at 70/70/70 + with the right gear, 12,000,000/50 = 240, 240 hours per skill, 240 / 5 = 48 days per 99, 48*3 = 144 days for max.
I had him hired and he left half way through an order because he "Felt pressured" bare in mind he had plenty of time to do the order, good luck anyway @Greendude
I mean it isn't exactly hard to use google...
https://www.oracle.com/technetwork/java/javase/downloads/jre8-downloads-2133155.html
Clear your cache download that, make sure you turn auto updates off if you don't want it to update.