Can I change my stance on the topic after favouring one initially?

Yes and no. It is not a good idea to alter your mind about an issue. Taking a stand and then changing your mind will get you into problems. If you’re unsure, it’s best to remain silent and wait for further information before taking a stand. It’s possible that shifting your attitude will be interpreted as ineptness. So, if you’re genuinely certain that you should alter your mind on the subject, say that your perspective was valid in context but that you want to agree with a different and contradictory point of view in general.