Page 5 of the datasheet states that the voltage level for SPI/I2C is 1.5V to 5V does it mean that if we apply 1.5V we select i2C mode and if we apply 5V we select SPI mode?

No, the range described on page 5 outlines the appropriate range for logic levels. To select SPI you should pull pin SPI/12C high and to select I2C pull the pin low as seen in the typical application circuit

Tags: KA-05063 SPI/I2C MAX14661ETI+ MAX14661