The general custom is that tzitizt are left completely undone on the sides. The question is soemtimes asked of garments like dress suits which are split in the back (or some kapotas which have a slit in the back) whether these would need tiztiz as they have four corners opposing each other (as opposed to other suits/shirts where the four corners- i.e. the tail and the collar) and thus would seem to indicate that they fall under the need to attact tzitzit. The general ruling here is that if the split is less than 1/2 of the garment, then we do not need to attach tzitzit- thus exempting these suit jackets and kapotas. The question can then be asked if we can attach tzitzit if we choose- and here opinions vary, though the consensus appears to be that since these garments do not fall into the halachic definition of a garment to which we need to apply tzitzit, if we did, we would not say a brachah when putting them on.
The Shulkhan Aruch haRav rules (Seif 16 that more than half split- they are required to have tzitzit, less than half split they are exempt and we do not attach tzitzit- 50/50 we attach tzitzit l'chumra but do not say a bracha and we do not wear them on shabbat. I'll check when I get home ont he rest, that is all I had on-hand
In the case of tzizit we find in stores, the split is quite high thus making them fall into the halachic definition of a garment on which we can say the brachah. (Or at least it is on the "ner tzitzit", the only make I have seen do this). When it comes to buttoning it, the buttons would still need to leave enough of a split for the garment to fall into the category of a garment on which we can say the brachah. My advice- take the garment in question to your local Rabbi and ask him for a definitive answer- one should always go by the ruliong of your Rabbi, rather than relying on answers from people that are unknown to you
edit: Ok, at home and I have checked both shulkhan aruch haRav and Mishna Berurah. In Shulkhan Aruch haRav Perek 10 seif 17 he discusses that one should not have hooks on the bottom half to hold the tzitzit closed if it requires an action to undo them. Similarly the Mishnah Berurah on Perek 10 seif 8 states that if there are hooks below the halfway mark that require an action to undo, they would be considered a closing and the garment coulds not have tzitzit or have a brachah said on it. neither directly addresses the issue of buttons- but since buttons perform the same action as the hooks in the given seif (keep the garment closed until it is specifically undone), having them on the bottom half of the garment would most likely be forbidden if you wanted to have tzitzit attached and to say a brachah. My advice- if you have such a garment take it to your local Orthodox Rabbi to get a proper ruling