Please help me answer this question. Thank you so much !!

Q1. (On-the-run bond off-the-run bond) U.S. treasury securities are one of the most important assets in the market to build well-diversified portfolios. The treasury securities are auctioned and sold only to limited big players. One of the interesting facts in the market, especially back in 80's and 90's, is that newly-issued (Treasury) bonds are traded at higher prices (meaning low yield). This means that even if coupon rates are the same, 25-year U.S. 4% semi-annual coupon Treasury bond that was issued 5 years ago is traded cheaper than 20-year U.S. 4% semi-annual coupon Treasury bond that was just issued. [In the market, newly-issued bonds are called on-the-run bonds and previously-issued bonds are called off-the-run bonds.] One explanation for this phenomenon is that investors value on-the-run bonds more as they are more liquid. This explanation is not perfect as this can be a circular logic: They are liquid because people love them. The reason for this love is unclear). Regardless of this argument on liquidity, is there any way that you can profit from this phenomenon? Come up with a way that does not require any risk to profit