HELP!!!3.5 year old; only child...toddler misbehaving?

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Literally I'm at my ends. My ex husband and I split up technically over 3 years ago but we recently tried reconciling and things didn't work out around 5 months ago but she didn't start exhibiting poor behavior until recently. She is a little raccoon. She is contantly getting into things. Tearing up stuff like paper, food, getting out clothes and shoes, writing on walls or couches if she gets something in her paws, getting into things without asking, doing things that she knows she shouldn't like my work badges, school things and different things like that. Shes not being respectful to my authority or her daycare at school. I started school in January but I was also staying at my sisters half the week a little before that to watch my new born nephew since she came down ailment that is still getting better.(which I don't anymore). I do tend to study in the evening and I feel we get quality time and she gets attention. She's very clingy when it comes to me and has always been that way since she was a baby newborn(breastfed). I just don't know how to make her mind she was a very well behaved child and laid back as well. Now it just makes me hate coming home because she is consistently destrustive disrespectful and literally thinks it's a joke . She knows she's doing wrong and either cries or just doesn't look at me when I get on her I feel like I've tried everything spanking,time out, doing both. I feel like I'm always giving the negative attention instead of positive. I've tried talking to her asking her if she happy or if she's mad at me or if she's sad or mad for a certain reason . Any advice or comfort is accepted I am on my last leg I hate being a single mother and it's worse because she can't behave.