Wow, Harris couldn't have said, I will return to the Obama border policies?

She could have said it, but it's not likely to have been very effective. She's part of the Administration - the overwhelming majority of voters will end up associating her with whatever the Administration has been doing anyway. Plus, voter perception of Democrats in general on immigration and border issues was very bad, making it an uphill climb for her to change their minds on it.

Do voters know who Obama is?

Yeah, the guy who screwed up the border before Trump took over. I doubt there are many voters who could accurately tell you the difference between Obama and Biden's border policies, and I doubt there are very many voters who are unhappy with Biden's performance on the border who would think fondly of Obama's. Voters are mostly (and rationally) ignorant of the details of candidates' actual positions or records.

If the Dems honored the nomination process, Harris wins?

She's the favorite, yes. She's the incumbent Vice President, has the enormous fundraising powers and free press that comes with it. Unlike in 2016, there was no obvious alternative in waiting that the party would consolidate around. So the most likely outcome of a primary is that she wins it. I think you're misreading what Pelosi said - she said that Harris would have been stronger if there had been a full open primary, and that she would have done well in the primary.