tyre replacement 4x4

[graemes75]

Hi, I have a Toyota Granvia 4x4 3.0 turbo diesel. I am looking at replacing the front two tyres as they have a considerable amount more wear, especially on the shoulders of the tyres.

I have been looking at replacing them with the same tyres that are currently on all the wheels but I have read a lot of conflicting advice regarding this.

1) Is it 100% yes that the tyres must be the same make?, obviously they will be the exact same size.

2) What are the "dangers" regarding having half worn ,4mm tread depth on the back and brand new ,8mm different brand of tyres on the front?

3) What would be the best considering the cost , and quality of the tyre?

Size - 225/70/15

Thanks in advance