I want to combine the spell "increased reflexes" with the spell "increased attribute (reaction)". The spell description of increased reflexes mentions that is incompatible with other increased to initiative and increased reaction also increases initiative. But was this the intention of the spell to prevent this combination or does it only means that it is incompatible with implants etc. that also gives additional actions? If the first version applies, this would also mean that the adept power "increased reaction" wouldn´t count. It this so?

I think ur mixing up Increased (as spells ) and Improved ( as powers ).

That is the problem i´m talking about. I´ll make an example with an Norm-Character (Human). Max. Reaction is 6, max. modified reaction is 9. If you give him the adept power increased reflexes at rating 3 it adds 3 to the characters reaction (maximum). The SPELL only adds 3 to initiative, NOT to reaction. So theoretically you could increase your reaction with the spell "increase reaction" to the augmented max. of 9 and THEN you could add the SPELL "increased reflexes". But if you increase your reaction (no matter if with the "augmented attribute" spell or adept power) you also change your initiative with the higher reaction. And ´flexboosters of any kind (adept power/cyber/spell) don´t work with ANY other kind of initiative-boosting add-on. So this would - theoretically - imply that you can´t have increased reflexes (no matter which rating or cource) and increased reaction (also no matter from where you get them and at which rating) together. True or not?

Increase Reflexes, the spell, is not described as incompatible with other means. Improved Reflexes is on the other hand. So u can cast an Increased reflexes on an adept with Improved reflexes and the higher rating will override the other. U can use Increased reflexes with Increased reaction or Improved reaction, but as far as Improved reflexes is concerned u can't combine it with tech/magic effects that boost init, as u said.

I think it has to do with the intent of the spell and it's target attribute. Using 'ware as an example. Reaction enhancers (that oviously inrease the reaction...which HAPPENS to affect initiative) is compatible with wired reflexes (which is INTENDED to increase initiative and HAPPENS to inrease reaction). The part that stands out...anything that increases the number of IP you have is not compatible with anything else that increases IP.

I'm fairly certain even those don't work together. SR4 seems to define 'initiative enhancement' as anything that affects Reaction, Intuition, Initiative or Initiative Passes, and nothing that affects any of them are compatible (IIRC there's one booster for reaction that doesn't state it's incompatible, but all the other ones do, so it may as well be...)