Module development and code questions

Hey.
I'm developing a new payment gateway to plug into ecommerce (Paystation - 3rd party CC processing) but testing is annoying because any time there is a failure, my shopping cart has been emptied.

I follow through the flow and see that in all cases the cart is cleared (and put into a 'transaction') prior to going off to any of the payment methods. So OK. There's probably a reason for that.

I do see that these dropped transactions sit in the user transaction store/history with status 'pending'. Makes sense as a fallback, I guess.

I can redirect the user to view that stalled order - but they cannot change it - only pay it - and can't even cancel it, although it would seem they can attempt to pay again.

SO ... does it make any sense for me to re-construct the shopping cart for failed transactions? I think I can see the bits I need, although there seems to be no handy transaction_load() function to use.

Alternatively (or as well) where is the appropriate hook to flag an error warning the user "You have unpaid orders awaiting payment"? Especially on the store_invoice page. I guess I can do it in the theme, but that doesn't seem quite right.

Hi! I have troubles with redirecting user after he has been registered. I've created custom module that register user, but I don't know how to redirect him to a specific page, or what to use to login the user. I tried with drupal_goto(), but all I get was access denied, probably because the user is not logged in. Can somebody tell me what to use to login user.
Thanks

I dont think it is possible now but i would like to give different cron intervals to different modules. is that possible now? if not can some one create such feature?

Do you happen to know how the publishing options are to be implemented in a new node type module.

My custom module (for a new bespoke node type that we can call "cow") uses hook_view for the default view. However a new cow node can be viewed by an anonymous user independently of whether it is set to be published or not.

I just can't find where the published or not check takes place and from there figure out if I'm supposed to do the check in my module or if the module is supposed to inherit the functionality from node.module somehow.

I have been trying to work on a site that would allow me to track some simple exercises so that I can pull data in the future and track their progress. I have look into using certain CCK modules but have experienced a lot of problems with them. So my first question is how would I start to set up a site that would allow a user to click on a workout, such as running, and then allow them to enter in their time,location,and heart rate. Then after that information was logged how would I allow them to query that data to bring up all pervious workouts under the same title?

If I have 5.x installed will a module for an older version work?