There are a bunch of things that I'm getting confused about and while I've researched online for resources to get clarification, I'm still not certain about the answers. So hoping to get some assistance from the experts

1.) can we manually select a regression model that has no constant term? e.g. we have a dataset and we get a model with constant term, but that model is found to be not so good for forecasting/prediction. Then another model is produced but with no constant term - is that possible?

2.) if 1 is possible, then what are the implications of having a no constant term model?

3.) if the data is time series, what impact does the drift have on the forecast? i'm trying to understand what drift really is.

e.g. forecasting savings balance for a portfolio of bank customers and forecasting yield on a product offered by the bank, the model produced "has a drift" - what exactly does that mean, what are its implications and how do we rectify this (e.g. having no constant term?)

thank you a ton